With more than 300,000 Nissan Leaf electric cars on the road, some more than six years old, battery degradation is becoming more and more of an issue.

The different rates of capacity loss are a topic of much discussion among Leaf owners, but it now seems likely that Nissan's choice of passive air cooling rather than active liquid cooling has contributed to faster capacity loss than in GM or Tesla electric cars.

Now Nissan has announced a new option for Leaf owners, one that's considerably less expensive than buying a new battery pack off the shelf for an aging Leaf.

That's substantially lower than the costs of new replacement batteries: 650,000 yen ($6,130) for 24-kilowatt-hour packs; 800,000 yen ($7,540) for 30-kwh packs; and 820,000 yen ($7,730) for the latest 40-kwh packs used in the 2018 Nissan Leaf.

The trade-in program will start in May, and thus far it's limited to Leaf owners within Japan.

The old Leaf battery packs will be inspected and refurbished as required to replace defective cells and modules by 4R Energy Corp, a joint venture between the carmaker and giant Japanese trading company Sumitomo.

While used electric-car batteries are expected to hold value on the secondary market for energy storage and other uses, Nissan has a different goal in mind.

2013 Nissan Leaf, Nashville area test drive, April 2013

In a statement, the company said that by reclaiming and refurbishing used battery packs, it can not only lower the cost of battery replacements but also "heighten the used-car value of electric vehicles."

That will, the company said, make owning electric cars more appealing and lead to greater sales for the zero-emission vehicles that will reduce carbon-dioxide emissions associated with personal transportation.

Green Car Reports reached out to Nissan North America for comment on the announcement and its relevance to North American customers. We received the following statement from its EV communications manager, Jeff Wandell.

"While we’re always looking at new ways to bring value to our customers, currently we don’t have any announcement to make at this time regarding a similar program for the U.S."